Analysis of mechanical properties of composite-metal bolted panel under thermo-mechanical coupling condition

With the continuous increase in the proportion of composite materials used in aircraft structures, a large number of composite-metal hybrid joint structures will appear. Due to the differences in thermal expansion coefficients of materials, hybrid structures will generate significant thermal stress in extreme temperature environments. This thermal stress, acting in superposition with external mechanical loads, will directly affect the structural strength of the aircraft. This study takes a multi-riveted composite panel with metal stiffeners as the research object and investigates its mechanical behavior under thermo-mechanical coupling. In the experimental aspect, three types of test schemes were designed, including room temperature tensile, pure temperature, and thermo-mechanical coupling. By analyzing strain data from different measurement points, the thermal stress distribution pattern of the panel structure was obtained. In the simulation aspect, the finite model of the structure was established by using the shell-beam combination unit. The thermal strain and bolt load distribution under different test conditions were acquired, showing good consistency with experimental results and thereby validating the model accuracy. Furthermore, a progressive damage analysis model considering damage in both composite materials and aluminum alloy was constructed to investigate the influence of thermal stress on the static strength of the structure. The results indicate that the failure of this panel is primarily triggered by extensive damage in the composite skin; low temperature (−55 ℃) causes a 6.49% reduction in the failure load, while high temperature (74 ℃) leads to a 5.75% increase. When the skin and stringer materials are swapped, structural failure is dominated by damage in the aluminum alloy skin. In this case, although thermal stress causes premature plastic deformation, it has minimal impact on the ultimate load-bearing capacity of the structure.